gschur

Description

This function is obsolete and is now included in the schur function. In most cases the gschur function will still work as before, but it will be removed in the future release.

The first three syntaxes can be replaced by

[As,Es]=schur(A,E)
[As,Es,Q,Z]=schur(A,E);Q=Q' //NOTE THE TRANSPOSITION HERE
[As,Es,Z,dim] = schur(A,E,flag)

The last syntax requires little more adaptations:

if

extern is a scilab function the new syntax should be [As,Es,Z,dim]= schur(A,E,Nextern) with Nextern defined as follow:

function t=Nextern(R)
if R(2)==0 then
  t=extern([1,R(1),R(3)])==1
else
  c=(R(1)+%i*R(2))/R(3)
  t=extern([2,real(c+c'),real(c*c')])==1
end
endfunction

if

extern is the name of an external function coded in Fortran or C the new syntax should be [As,Es,Z,dim]= schur(A,E,'nextern') with nextern defined as follow:

logical function nextern(ar, ai, beta)
double precision ar,ai,beta
integer r,extern
if (ai.eq.0.0d0) then
  r=extern(1,ar,beta,0.0d0,0.0d0)
else
  r=extern(2,0.0d0,0.0d0,2.0d0*ar,ar*ar+ai*ai)
endif
nextern=r.eq.1
end

See Also

• external — Objet Scilab, fonction externe ou routine
• schur — [ordered] Schur decomposition of matrix and pencils